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;;; puny.el --- translate non-ASCII domain names to ASCII
;; Copyright (C) 2015-2020 Free Software Foundation, Inc.
;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
;; Keywords: mail, net
;; This file is part of GNU Emacs.
;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;; Written by looking at
;; http://stackoverflow.com/questions/183485/can-anyone-recommend-a-good-free-javascript-for-punycode-to-unicode-conversion
;;; Code:
(eval-when-compile (require 'cl-lib))
(require 'seq)
(defun puny-encode-domain (domain)
"Encode DOMAIN according to the IDNA/punycode algorithm.
For instance, \"fśf.org\" => \"xn--ff-2sa.org\"."
;; The vast majority of domain names are not IDNA domain names, so
;; add a check first to avoid doing unnecessary work.
(if (string-match "\\'[[:ascii:]]+\\'" domain)
domain
(mapconcat 'puny-encode-string (split-string domain "[.]") ".")))
(defun puny-encode-string (string)
"Encode STRING according to the IDNA/punycode algorithm.
This is used to encode non-ASCII domain names.
For instance, \"bücher\" => \"xn--bcher-kva\"."
(let ((ascii (seq-filter (lambda (char)
(< char 128))
string)))
(if (= (length ascii) (length string))
string
(concat "xn--"
(if (null ascii)
""
(concat ascii "-"))
(puny-encode-complex (length ascii) string)))))
(defun puny-decode-domain (domain)
"Decode DOMAIN according to the IDNA/punycode algorithm.
For instance, \"xn--ff-2sa.org\" => \"fśf.org\"."
(mapconcat 'puny-decode-string (split-string domain "[.]") "."))
(defun puny-decode-string (string)
"Decode an IDNA/punycode-encoded string.
For instance \"xn--bcher-kva\" => \"bücher\"."
(if (string-match "\\`xn--" string)
(condition-case nil
(puny-decode-string-internal (substring string 4))
;; If the string is invalid Punycode, just return the string.
(args-out-of-range string))
string))
(defconst puny-initial-n 128)
(defconst puny-initial-bias 72)
(defconst puny-base 36)
(defconst puny-damp 700)
(defconst puny-tmin 1)
(defconst puny-tmax 26)
(defconst puny-skew 28)
;; 0-25 a-z
;; 26-36 0-9
(defun puny-encode-digit (d)
(if (< d 26)
(+ ?a d)
(+ ?0 (- d 26))))
(defun puny-adapt (delta num-points first-time)
(let ((delta (if first-time
(/ delta puny-damp)
(/ delta 2)))
(k 0))
(setq delta (+ delta (/ delta num-points)))
(while (> delta (/ (* (- puny-base puny-tmin)
puny-tmax)
2))
(setq delta (/ delta (- puny-base puny-tmin))
k (+ k puny-base)))
(+ k (/ (* (1+ (- puny-base puny-tmin)) delta)
(+ delta puny-skew)))))
(defun puny-encode-complex (insertion-points string)
(let ((n puny-initial-n)
(delta 0)
(bias puny-initial-bias)
(h insertion-points)
result m ijv q)
(while (< h (length string))
(setq ijv (cl-loop for char across string
when (>= char n)
minimize char))
(setq m ijv)
(setq delta (+ delta (* (- m n) (+ h 1)))
n m)
(cl-loop for char across string
when (< char n)
do (cl-incf delta)
when (= char ijv)
do (progn
(setq q delta)
(cl-loop with k = puny-base
for t1 = (cond
((<= k bias)
puny-tmin)
((>= k (+ bias puny-tmax))
puny-tmax)
(t
(- k bias)))
while (>= q t1)
do (push (puny-encode-digit
(+ t1 (mod (- q t1)
(- puny-base t1))))
result)
do (setq q (/ (- q t1) (- puny-base t1))
k (+ k puny-base)))
(push (puny-encode-digit q) result)
(setq bias (puny-adapt delta (+ h 1) (= h insertion-points))
delta 0
h (1+ h))))
(cl-incf delta)
(cl-incf n))
(nreverse result)))
(defun puny-decode-digit (cp)
(cond
((<= cp ?9)
(+ (- cp ?0) 26))
((<= cp ?Z)
(- cp ?A))
((<= cp ?z)
(- cp ?a))
(t
puny-base)))
(defun puny-decode-string-internal (string)
(with-temp-buffer
(insert string)
;; The encoded chars are after any final dash, else the whole string.
(let ((encoded (buffer-substring
(if (search-backward "-" nil 'move)
(1+ (point))
(point))
(point-max)))
(ic 0)
(i 0)
(bias puny-initial-bias)
(n puny-initial-n)
out)
(delete-region (point) (point-max))
(while (< ic (length encoded))
(let ((old-i i)
(w 1)
(k puny-base)
digit t1)
(cl-loop do (progn
(setq digit (puny-decode-digit (aref encoded ic)))
(cl-incf ic)
(cl-incf i (* digit w))
(setq t1 (cond
((<= k bias)
puny-tmin)
((>= k (+ bias puny-tmax))
puny-tmax)
(t
(- k bias)))))
while (>= digit t1)
do (setq w (* w (- puny-base t1))
k (+ k puny-base)))
(setq out (1+ (buffer-size)))
(setq bias (puny-adapt (- i old-i) out (= old-i 0))))
(setq n (+ n (/ i out))
i (mod i out))
(goto-char (point-min))
(forward-char i)
(insert (format "%c" n))
(cl-incf i)))
(buffer-string)))
;; http://www.unicode.org/reports/tr39/#Restriction_Level_Detection
;; http://www.unicode.org/reports/tr31/#Table_Candidate_Characters_for_Inclusion_in_Identifiers
(defun puny-highly-restrictive-string-p (string)
"Say whether STRING is \"highly restrictive\" in the Unicode IDNA sense.
See http://www.unicode.org/reports/tr39/#Restriction_Level_Detection
for details. The main idea is that if you're mixing
scripts (like latin and cyrillic), you may confuse the user by
using homographs."
(let ((scripts
(delq
t
(seq-uniq
(seq-map (lambda (char)
(if (memq char
;; These characters are always allowed
;; in any string.
'(#x0027 ; APOSTROPHE
#x002D ; HYPHEN-MINUS
#x002E ; FULL STOP
#x003A ; COLON
#x00B7 ; MIDDLE DOT
#x058A ; ARMENIAN HYPHEN
#x05F3 ; HEBREW PUNCTUATION GERESH
#x05F4 ; HEBREW PUNCTUATION GERSHAYIM
#x0F0B ; TIBETAN MARK INTERSYLLABIC TSHEG
#x200C ; ZERO WIDTH NON-JOINER*
#x200D ; ZERO WIDTH JOINER*
#x2010 ; HYPHEN
#x2019 ; RIGHT SINGLE QUOTATION MARK
#x2027 ; HYPHENATION POINT
#x30A0 ; KATAKANA-HIRAGANA DOUBLE HYPHEN
#x30FB)) ; KATAKANA MIDDLE DOT
t
(aref char-script-table char)))
string)))))
(or
;; Every character uses the same script.
(= (length scripts) 1)
(seq-some 'identity
(mapcar (lambda (list)
(seq-every-p (lambda (script)
(memq script list))
scripts))
'((latin han hiragana kana)
(latin han bopomofo)
(latin han hangul)))))))
(defun puny-highly-restrictive-domain-p (domain)
"Say whether DOMAIN is \"highly restrictive\" in the Unicode IDNA sense.
See `puny-highly-restrictive-string-p' for further details."
(seq-every-p 'puny-highly-restrictive-string-p (split-string domain "[.]")))
(provide 'puny)
;;; puny.el ends here
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